Related question: Did Romans even have any way of diagnosing arteriosclerosis? Did they even perform something like an autopsy if someone died of heart failure?

Friends: a gentle reminder that this is /r/AskHistorians and not /r/AskScience. This question is interested in what people believed about nutrition and its relationship to health at the time of Claudius. The modern understandings of the same fall outside the /r/AskHistorians remit. If you are prepared to answer this question historically, please remember that our answers are required to be detailed, and our users enforce this with downvotes and reports far more ruthlessly than the mods do (although we're pretty ruthless too).

Thank you kindly.

Another related question: Did doctors know this in the early 1930's when Robert Graves wrote the book? Was it common knowledge?